Methods for processing biological specimens by laser microdissection have existed since the mid-1970s and have been continually refined since then.
In laser microdissection, cells, tissue regions, and so forth can be isolated from an object to be dissected by a laser beam and recovered as so-called “dissectates.” A particular advantage of laser microdissection is the brief contact between the object and the laser beam, causing very little modification to the object. Specific recovery of the dissectates can be accomplished in a variety of ways.
In known methods, for example, a dissectate can be isolated from an object by means of an infrared or ultraviolet laser beam; the dissectate falls in response to gravity into a suitable dissectate collection container. The dissectate can also be excised from the object together with an adhering membrane. In “laser capture microdissection,” on the other hand, a thermoplastic membrane is heated by means of a corresponding laser beam; the membrane fuses with the desired region of the object and can be removed in a subsequent step by tearing. A further alternative consists in attaching the dissectate, by means of the laser beam, to a cover of a dissectate collection container. With known inverted microscope systems for laser microdissection, dissectates catapulted upward can also be attached to the bottom of a dissectate collection container which is equipped with an adhesive coating.
In laser microdissection, processing of the objects very seldom occurs entirely manually. It is typical in microdissection that the object to be dissected is captured in image-producing manner, preferably digitally, and displayed e.g. on a monitor. As is known in principle, a user can, by means of a user interaction unit, for example by means of a PC system, define on a correspondingly reproduced object image a cutting line specification along which a laser microdissection is to be performed. It is also possible, however, to evaluate corresponding object images entirely automatically, for example using known contrast detection methods and/or pattern recognition methods, so that cutting line specifications can be defined automatically. Reference is made, for example, to WO 2005/040762 A1 for details. When the “defining of a processing specification” on the basis of an object image is discussed in the context of embodiments of the present invention hereinafter, both possibilities are to be encompassed by the wording. The object to be dissected is then dissected in accordance with the processing specification, for example a manual cutting line specification, that has been defined.
The principal disadvantage of the method discussed above, i.e. the respectively alternating definition of processing specifications, for example manual cutting line specifications, and subsequent processing, is in particular the large expenditure of time associated therewith. Cutting line specification by a user often requires appreciably more time than the subsequent actual laser microdissection. The same also applies to automatic methods, since the detailed image evaluation necessary for this requires considerable time even in modern evaluation systems.